LED lamps are more energy-saving and environment friendly than traditional fluorescent lamps and incandescent lamps, and thus LED lamps are replacing the current fluorescent lamps and incandescent lamps. In incandescent lamps with a TRIAC dimmer, it is also expected to be replaced by LED lamps, and thus LED needs a compatible TRIAC dimmer. However, when the LED lamps replace incandescent lamps, since when the TRIAC is turned on, the voltage at its output terminal will have great voltage change rate (dv/dt), great surge current will be generated at the input terminal. The surge current has great shock amplitudes, and the duration time is short, easy to cause erroneous turning-off of TRIAC, affect the stable work of the LED driving circuit, make the LED lamp flicker; in addition, the input current of the TRIAC device needs to be greater than its maintaining current; when the input current is smaller than the maintaining current, it is easy to turn off TRIAC, which also causes the flickering of the LED. In order to solve the above technical problem, the prior art uses the following solution, but still has certain technical defects.
The circuit principle diagram as shown in FIG. 1 shows a prior art bleeder circuit, i.e., a Current source I10 and a regulating tube M00 are connected in series to form a bleeder circuit, and the current source I10 may be replaced by a resistor. When the TRIAC dimmer is turned on, it is difficult for the linear LED driving circuit current to achieve the maintaining current of the TRIAC dimmer, the regulating tube M00 of the bleeder circuit is turned on, and the bleeder circuit generates bleeder current iblr, to make the input current achieves the maintain current. FIG. 2 shows waveforms the input voltage vin and the input current iin, and the shadow part is the current generated by the bleeder circuit, and this part of bleeder current will generate additional power consumption. Moreover, the bigger the turning-on angle of the TRIAC dimmer is, the longer time t1 that the bleeder circuit generates the bleeder current iblr is, and the bigger the power consumption is, the lower the conversion efficiency is.